Good Neighbour Campaigns

Tree Lichen Monitoring

Tree lichen monitoring is a simple, cost-effective, and scientific way to have community members gauge the current state and annual progress of their area’s air quality. 

Relying on the relationship between ambient air quality levels and two species of tree lichen (root-less, moss-like organisms which tend to thrive in areas with low sulphur dioxide and nitrogen dioxide), this technique consists of using a simple hand-made measuring tool to visually identify and gauge the presence of Candelaria concolor and Physcia millegrana on both maple and ash trees. The more of these species of lichen present, the better the area’s air quality.

The Science

This tactic utilizes the methodology of Dr.George Sorger, a  professor at McMaster University in Hamilton.  Testing both Ash and Maple trees, Sorger found that there existed a relationship between lichen presence (specifically two types: Physcia Millegrana and Candelaira Colcolor) and Sulphur Dioxide (SO2) and Nitrogen Dioxide (NO2) levels. He found that areas with high SO2 and NO2 had low to non-existent levels of lichen present, and areas with low levels of SO2 and NO2 had high levels of lichen present. Given that SO2 and NO2 are good indicators of airborne pollution, we can assume that areas with a high lichen presence have better air quality than those with a low lichen presence.


As a follow-up to the white flag campaign, the Hamilton GNC saw this method as a great way to lend more of a scientific backing to the claim that AM-Dofasco is having a negative impact on its neighbours’ air quality. It was also seen as a simple and cost-effective way to continue to build capacity in neighbourhoods looking to gauge and track their air quality. From late November 2010 to May of 2011, the campaign trained approximately 144 high school students and residents across Hamilton. The initiative resulted in a city-wide community-driven study that was able to identify pollution patterns and pollution hotspots (the majority of which were located in neighbours adjacent to industry). 

Resources, Materials, and Results

View Lichen Pollution Monitoring – Good Neighbour Campaign in a larger map